Fw: Giant Crater Found: Tied to Worst Mass Extinction Ever

news.yahoo.com/s/space/20060602/sc_space...stmassextinctionever

An apparent crater as big as Ohio has been found in Antarctica. Scientists think it was carved by a space rock that caused the greatest mass extinction on Earth, 250 million years ago.

The crater, buried beneath a half-mile of ice and discovered by some serious airborne and satellite sleuthing, is more than twice as big as the one involved in the demise of the dinosaurs.

The crater's location, in the Wilkes Land region of East Antarctica, south of Australia, suggests it might have instigated the breakup of the so-called Gondwana supercontinent, which pushed Australia northward, the researchers said.

"This Wilkes Land impact is much bigger than the impact that killed the dinosaurs, and probably would have caused catastrophic damage at the time," said Ralph von Frese, a professor of geological sciences at Ohio State University.

How they found it

The crater is about 300 miles wide. It was found by looking at differences in density that show up in gravity measurements taken with NASA's GRACE satellites. Researchers spotted a mass concentration, which they call a mascon—dense stuff that welled up from the mantle, likely in an impact.

"If I saw this same mascon signal on the Moon, I'd expect to see a crater around it," Frese said. (The Moon, with no atmosphere, retains a record of ancient impacts in the visible craters there.)

So Frese and colleagues overlaid data from airborne radar images that showed a 300-mile wide sub-surface, circular ridge. The mascon fit neatly inside the circle.

"And when we looked at the ice-probing airborne radar, there it was," he said today.

Smoking gun?

The Permian-Triassic extinction, as it is known, wiped out most life on land and in the oceans. Researchers have long suspected a space rock might have been involved. Some scientists have blamed volcanic activity or other culprits.

The die-off set up conditions that eventually allowed dinosaurs to rule the planet.

The newfound crater is more than twice the size of the Chicxulub crater in the Yucatan peninsula, which marks the impact that may have ultimately killed the dinosaurs 65 million years ago. The Chicxulub space rock is thought to have been 6 miles wide, while the Wilkes Land meteor could have been up to 30 miles wide, the researchers said.

Confirmation needed

Postdoctoral researcher Laramie Potts assisted in the discovery.

The work was financed by NASA and the National Science Foundation. The discovery, announced today, was initially presented in a poster paper at the recent American Geophysical Union Joint Assembly meeting in Baltimore.

The researchers say further work is needed to confirm the finding. One way to do that would be to go there and collect rock from the crater to see if its structure matches what would be expected from such a colossal impact.

That's a great bit of detective work there!

Bart.

An apparent crater as big as Ohio has been found in Antarctica. Scientists think it was carved by a space rock that caused the greatest mass extinction on Earth, 250 million years ago.

Very interesting if proved to be an impact crater and the cause (or part cause) of the Permian extinction but other large circular basins have been discovered in the Falkland Plateau and off northwestern Australia dating to the late Permian period (with no firm evidence as yet that they are impact craters) so I guess it's a matter of waiting to see what further investigation reveals with this particular basin.

30km wide wow!! I'm pretty sure that if we were alerted to an NEO that large on a collision course even with a decades notice, there is absolutely nothing we could do about it. I'm pretty sure civilisation as we know it would break down long before the impact as law and order, economies etc would fall apart as anarchy took hold.

Another though crossed my mind, were all familiar with drakes equation which calculates the likelyhood of ET phoning us etc. One of the fudge factors is of course how long a race survives. I would speculate that in a solar system where planets form there is a high likelyhood (if not certaintly) that objects such as asteroids/comets will exist too and that given a long enough period something large enough to cause mass extinction events would collide with ET's home planet. Given that, would it be fair to say that the value of this factor musn't be very high at all. i.e. if they dont wipe themselves out nature will do the job eventually.

Another though crossed my mind, were all familiar with drakes equation which calculates the likelyhood of ET phoning us etc. One of the fudge factors is of course how long a race survives. I would speculate that in a solar system where planets form there is a high likelyhood (if not certaintly) that objects such as asteroids/comets will exist too and that given a long enough period something large enough to cause mass extinction events would collide with ET's home planet. Given that, would it be fair to say that the value of this factor musn't be very high at all. i.e. if they dont wipe themselves out nature will do the job eventually.

This is related to a point David Bell makes in a talk he gives. One piece of his argument is that without the Moon we would take a lot more hits, an ET's planet without a big closeby moon would be a much easier target for asteroids.

Then again we can't say how common asteroid belts are in systems. They seem to pose a bigger risk than comets.

This is related to a point David Bell makes in a talk he gives. One piece of his argument is that without the Moon we would take a lot more hits, an ET's planet without a big closeby moon would be a much easier target for asteroids.

Albert, can you explain the rationale behind David Bell's argument. The Earth is about 80 times more massive than the Moon and 385,000 kms away. I just can't see how the Moon could be responsible for deflecting anything away from Earth.